GUARANTOR/NON-GUARANTOR FINANCIAL INFORMATION - Condensed Consolidated Statements of Comprehensive Income (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 24, 2016	Sep. 30, 2017	Sep. 24, 2016
Condensed consolidated financial information for the Company (Parent), the guarantor subsidiaries and the non-guarantor subsidiaries
Net earnings	$ 36,666	$ 29,521	$ 123,949	$ 107,134
Foreign currency translation adjustments:
Unrealized translation gain (loss)	19,530	770	60,471	(1,938)
Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Net of Tax		1,972
Derivatives used in Net Investment Hedge, Net of Tax, Period Increase (Decrease)	(740)	1,972	1,816	4,897
Gain/(loss) on hedging activities:
Amortization cost included in interest expense	19	18	56	56
Equity in other comprehensive income	0	0	0	0
Other comprehensive income (loss)	18,809	2,760	58,711	3,015
Comprehensive income	55,475	32,281	182,660	110,149
Comprehensive loss (income) attributable to noncontrolling interests	(2,570)	(1,618)	(4,552)	(5,732)
Comprehensive income attributable to Valmont Industries, Inc.	52,905	30,663	178,108	104,417
Eliminations
Condensed consolidated financial information for the Company (Parent), the guarantor subsidiaries and the non-guarantor subsidiaries
Net earnings	(38,160)	(22,645)	(100,715)	(78,753)
Foreign currency translation adjustments:
Unrealized translation gain (loss)	0	0	0	0
Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Net of Tax		0
Derivatives used in Net Investment Hedge, Net of Tax, Period Increase (Decrease)	0		0
Gain/(loss) on hedging activities:
Amortization cost included in interest expense	0	0	0	0
Equity in other comprehensive income	(18,418)	(500)	(60,017)	3,704
Other comprehensive income (loss)	(18,418)	(500)	(60,017)	3,704
Comprehensive income	(56,578)	(23,145)	(160,732)	(75,049)
Comprehensive loss (income) attributable to noncontrolling interests	0	0	0	0
Comprehensive income attributable to Valmont Industries, Inc.	(56,578)	(23,145)	(160,732)	(75,049)
Parent
Condensed consolidated financial information for the Company (Parent), the guarantor subsidiaries and the non-guarantor subsidiaries
Net earnings	35,208	28,173	119,851	103,168
Foreign currency translation adjustments:
Unrealized translation gain (loss)	0	0	0	0
Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Net of Tax		1,972
Derivatives used in Net Investment Hedge, Net of Tax, Period Increase (Decrease)	(740)		1,816
Gain/(loss) on hedging activities:
Amortization cost included in interest expense	19	18	56	56
Equity in other comprehensive income	18,418	500	60,017	(3,704)
Other comprehensive income (loss)	17,697	2,490	58,257	1,249
Comprehensive income	52,905	30,663	178,108	104,417
Comprehensive loss (income) attributable to noncontrolling interests	0	0	0	0
Comprehensive income attributable to Valmont Industries, Inc.	52,905	30,663	178,108	104,417
Guarantors
Condensed consolidated financial information for the Company (Parent), the guarantor subsidiaries and the non-guarantor subsidiaries
Net earnings	15,354	6,754	37,784	32,941
Foreign currency translation adjustments:
Unrealized translation gain (loss)	(3,613)	(114)	64,411	(263)
Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Net of Tax		0
Derivatives used in Net Investment Hedge, Net of Tax, Period Increase (Decrease)	0
Gain/(loss) on hedging activities:
Amortization cost included in interest expense	0	0	0	0
Equity in other comprehensive income	0	0	0	0
Other comprehensive income (loss)	(3,613)	(114)	64,411	(263)
Comprehensive income	11,741	6,640	102,195	32,678
Comprehensive loss (income) attributable to noncontrolling interests	0	0	0	0
Comprehensive income attributable to Valmont Industries, Inc.	11,741	6,640	102,195	32,678
Non- Guarantors
Condensed consolidated financial information for the Company (Parent), the guarantor subsidiaries and the non-guarantor subsidiaries
Net earnings	24,264	17,239	67,029	49,778
Foreign currency translation adjustments:
Unrealized translation gain (loss)	23,143	884	(3,940)	(1,675)
Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Net of Tax		0
Derivatives used in Net Investment Hedge, Net of Tax, Period Increase (Decrease)	0		0
Gain/(loss) on hedging activities:
Amortization cost included in interest expense	0	0	0	0
Equity in other comprehensive income	0	0	0	0
Other comprehensive income (loss)	23,143	884	(3,940)	(1,675)
Comprehensive income	47,407	18,123	63,089	48,103
Comprehensive loss (income) attributable to noncontrolling interests	(2,570)	(1,618)	(4,552)	(5,732)
Comprehensive income attributable to Valmont Industries, Inc.	$ 44,837	$ 16,505	$ 58,537	$ 42,371